The present invention relates to apparatus for handling generally flat, flexible web products and, more particularly, to apparatus for conveying the products along a product path, removing the products from the path, and stacking the products.
Various equipment has been devised in the past to convey, stack, and package flexible web products, such as plastic food bags. Typically, such bags are conveyed along a path by a belt conveyor, engaged by grippers carried on a rotary support and removed from the path, and then deposited on a surface where they are stacked prior to being packaged.
Various difficulties have been encountered in handling such web type products. Such a plastic bag may, for example, include a zipper locking mechanism and, additionally, it may be gusseted or include wing-shaped pouch portions. One bag of this type is shown in U.S. Pat. No. 4,358,466, issued Nov. 9, 1982, to Stevenson. Even in a flat, folded position, a bag of this sort varies in thickness. As a consequence, when the bag is to be engaged by a number of gripping type devices simultaneously, allowance must be made for such variations in the bag thickness.
U.S. Pat. No. 4,284,301, issued Aug. 18, 1981, to Geiger et al teaches utilizing a spring-loaded jaw which can close in a manner to compensate for varying thicknesses of articles engaged by the jaw. By this arrangement, a number of jaws can be closed simultaneously with the same actuator mechanism. One pair of jaws is designed to rigidly clamp the product, while at least one other jaw is spring-loaded so that it can close to a different degree to compensate for the varying product thickness. While providing some advantages, the Geiger et al '301 gripper arrangement is nevertheless subject to damage from jams since only a small amount of variation in gripper position is permitted by the spring arrangement and, further, since pivoting of the gripper jaws independently is possible only in one direction, that is, away from the opposing gripper jaw.
U.S. Pat. No. 4,381,056, issued Apr. 26, 1983, to Eberle discloses a double acting gripping mechanism in which a gripper finger, constructed of a strip of spring steel, can be deflected in either of two directions. Even a small force causes deflection of the finger arrangement of Eberle, however, with the deflection distance being dependent upon the spring constant of the finger. Additionally, the amount of deflection is the same in either direction for a given force.
While it may be desirable to provide a gripper finger mechanism which can deflect away from a co-acting anvil or gripper structure so as to accomodate products of different thicknesses and to provide a gripper finger which can deflect toward the anvil or opposing gripper finger so as to limit the amount of damage occurs when products jam in the product path, nevertheless it is not always desirable that the deflection should be initiated at even the slightest force level, nor is it desirable that the threshold force levels for deflection in either direction be the same. Further, it may be advantageous to limit the amount of deflection permitted. It is seen, therefore, that there is a need for a device for engaging articles of varying thickness, including a plurality of gripper jaws, in which the gripper jaws can deflect in either of two directions, with the threshold force required to initiate deflection differing, and with the range of motion permitted in the two directions also differing.